1. Field of the Invention
This invention pertains generally to fire suppression systems, and more particularly to a portable cold compressed air foam producing system.
2. Description of the Background Art
Fires do not occur very often in aviation operations but, when they do, such fires have the potential to become deadly very quickly. In recent years, the National Guard Aviation has approached new thresholds of exposure to loss of life and high dollar losses of military equipment. The National Guard now has the latest generation of military equipment, and most National Guard combat units train for combat anywhere on short notice. This increased tempo of training requires managing risk at a higher exposure level to ensure that soldiers and equipment are protected. The frequent and rapid refueling operations carried out by the National Guard Aviation presents a high risk of fires occurring due to spilled fuel on and around the flight line. Current portable fire suppression systems used by the National Guard Aviation employ various known chemical agents to suppress the fire such as CO.sub.2, Halon gas, and Dry Chemical (Purple K).
A typical CO.sub.2 system uses 25 lbs. of CO.sub.2 and has a shooting range of 45 feet for a duration of about 45 seconds. The problem most often encountered with those systems to suppress a fire is that the CO.sub.2 discharge is easily diffused by the wind, thus adversely affecting the intensity and direction of the CO.sub.2 spray. Also, CO.sub.2 systems do not provide flashback protection and the fire can be easily re-ignited if there is fuel remaining.
Halon gas systems suppress fire by removing the oxygen from the fire, thus extinguishing the fire by removing the oxidizer required for fire to burn. Typical Halon gas systems have a discharge range of approximately 50 feet for a duration of 90 seconds. As with the CO.sub.2 systems, Halon systems do not provide flashback protection. Another disadvantage of Halon systems is that Halon is not environmentally friendly as it destroys the earth's ozone layer, and thus cannot be released into the air at any time other than for actual fire suppression. This limitation prevents actual field training for use of the system. Also, Halon systems are mandated for replacement by the year 2003.
The typical Dry Chemical (Purple K) system has a range of 25 feet for a duration of 51 seconds. The disadvantages of such systems are that they do not provide flashback protection, are only fairly stable in windy conditions, are easily effected by age and humidity, and are difficult to service.
There are also foam expansion systems currently available. Such foam expansion systems produce "high energy" foam by injecting compressed air at ambient temperature into a water-foam concentrate solution to generate a volume of foam much greater than the volume of water. Conventional foam expansion systems generally use two different approaches to generate foam. One approach is to use an air aspirating nozzle and make the foam at the nozzle point. However, the use of ambient temperature air results in ambient temperature foam being produced. Another approach is to use a mixing manifold to combine compressed air with the solution upstream of the nozzle; however, such conventional systems introduce air in direction of flow that is perpendicular to the flow of solution. This approach adversely affects foam expansion and acceleration because the air does not negotiate right angle turns efficiently. The result is diminished foam expansion ratios and discharge distances. And, neither conventional system provides the capability to control or vary the moisture content of the foam produced for a specific application.
Accordingly, there is a need for a need for a portable cold foam producing fire suppression system for flammable liquid and structure fires, that has an extended discharge range and duration, that provides flashback protection, and that allows operator training using chemicals that are environmentally safe. The present invention satisfies this need, as well as others, and generally corrects the deficiencies found in the background art.